White light illumination system with narrow band green phosphor and multiple-wavelength excitation

ABSTRACT

A white light illumination system may comprise: a phosphor package; a first radiation source for providing co-excitation radiation to the phosphor package, the source emitting in wavelengths ranging from about 250 nm to about 410 nm; and a second radiation source for providing co-excitation radiation to the phosphor package, the source emitting in wavelengths ranging from about 410 nm to about 540 nm; wherein the phosphor package is configured to emit photoluminescence in wavelengths ranging from about 440 nm to about 700 nm upon co-excitation from the first and second radiation sources, and wherein the phosphor package comprises at least one narrow band green phosphor with a photoluminescence peak with a full width at half maximum of less than 60 nm, and wherein the narrow band green phosphor is configured to emit photoluminescence in wavelengths ranging from about 500 nm to about 550 nm.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 12/398,059 filed Mar. 4, 2009, which claims the benefit ofpriority to provisional application Ser. No. 61/034,699 filed Mar. 7,2008, which applications are incorporated herein by reference in theirentirety.

FIELD OF THE INVENTION

Embodiments of the present invention are directed in general to whitelight illumination systems with phosphor material including a narrowband green phosphor and multiple radiation sources for co-excitation ofthe phosphor material. More particularly, though not exclusively,embodiments of the invention concern white light illumination systemsfor color liquid crystal displays.

BACKGROUND OF THE INVENTION

Devices known as “white LED's” are relatively recent innovationsdesigned to replace the conventional incandescent light bulb. It was notuntil LED's emitting in the blue/ultraviolet region of theelectromagnetic spectrum were developed that it became possible tofabricate a white light illumination source based on an LED.Economically, white LED's have the potential to replace incandescentlight sources (light bulbs), particularly as production costs fall andthe technology develops further. In particular, the potential of a whitelight LED is believed to be superior to that of an incandescent bulb inlifetime, robustness, and efficiency. For example, white lightillumination sources based on LED's are expected to meet industrystandards for operation lifetimes of 100,000 hours, and efficiencies of80 to 90 percent. High brightness LED's have already made a substantialimpact on such areas of society as traffic light signals, replacingincandescent bulbs, and so it is not surprising that they will soonprovide generalized lighting requirements in homes and businesses, aswell as other everyday applications. The term “white LED” may besomething of a misnomer as no LED emits “white light,” but it is usedthroughout the art to describe a lighting system where a blue/UV LEDprovides energy to another component of the system, one or morephosphors, which emit light when excited by the pumping LED, and wherethe excitation radiation from the pumping LED is combined with the lightfrom the phosphor(s) to produce the final white light “product.”

As described in U.S. Pat. No. 7,476,338 to Sakane et al., there are inthe art generally two approaches to providing LED-based white lightillumination systems. In a conventional multi-chip type system the threeprimary colors are provided by red, green, and blue LEDs individually. Aone-chip system comprises a blue LED in conjunction with a phosphorwhere the blue LED serves two purposes: the first being to excite thephosphor, and the second to contribute blue light which is combined withthe light emitted by the phosphor to make the perceived white lightcombination.

According to Sakane et al. the one-chip type system has a preferablecharacteristic in that an LED-phosphor system can be dimensionallysmaller than a multi-chip system, and simpler in design because themultiple drive voltages and temperature considerations of multiple LEDsdo not have to be taken into account. Thus the cost to manufacture thesystem may be reduced. Further, by using a phosphor having a broademission spectrum, the white emission from the system betterapproximates the spectrum of sunlight, and thus the color renderingproperties of the system may be improved. For these reasons greaterattention has been given to the one-chip rather than multiple-chip typesystems.

The single-chip type systems may further be divided into two categories.In a first category, as alluded to earlier, light from a highluminescence blue LED and a phosphor emitting a yellow color as a resultof excitation from the blue LED is combined, the white luminescence ofthe combined light obtained by using a complementary relation betweenthe blue emission of the LED and the yellow emission of the phosphor. Inthe second category, the excitation source is an LED that emits in thenear-ultraviolet or ultraviolet (UV) region of the spectrum, and thelight from the phosphor package may include a blue-emitting phosphor,red-emitting phosphor, and green-emitting phosphor is combined to formwhite light. In addition to being able to adjust the color renderingproperties of the white light with this type of system, an arbitraryemission color may also be produced by controlling the mixing ratios ofthe red, green, and blue photoluminescence.

The benefits of these single-chip systems are well appreciated in theart, but so too are their drawbacks when it comes to enhancing colorrendering properties. For example, the white light emission from atypical one-chip system consisting of a blue LED and a yellow phosphor(such as YAG:Ce) is deficient in the longer wavelength side of thevisible spectrum, resulting in a bluish white light appearance. TheYAG:Ce yellow phosphor of the system does not help much in contributingto the needed 600 to 700 nm emission content, since its excitation bandwith the greatest efficiency is at about 460 nm, and the excitationrange of this yellow phosphor is not particularly broad. Furtherdisadvantages of this single-chip system are the disparities in theemission wavelength ranges of the blue LED, due in part to themanufacturing process, and if these deviate from the optimal excitationrange of the YAG:Ce-based yellow phosphor, there results a loss ofwavelength balance between the blue light and the yellow light.

There are also disadvantages to this second category of single-chipsystems. White light illumination formed by combining thephotoluminescence from a UV or near-UV excited red, green, and bluephosphor system is also deficient in the longer wavelengths because theexcitation and emission efficiencies of the red phosphor are lowercompared to that of the other phosphors in the package. The white LEDdesigner therefore may have little choices available other than toincrease the ratio of the red phosphor in the mixture relative to theblue and green phosphors. But this action may lead to an undesirableconsequence: the ratio of the green phosphor to the others may now beinsufficient and luminescence from the white LED may suffer. It wouldappear that a white color with high luminescence is difficult to obtain.And the color rendering properties are still nowhere near optimum as thered phosphor typically has a sharper emission spectrum than the others.

It is clear that multi-chip white light illumination systems suffer fromdisadvantages, not the least of which is a need for a plurality ofvoltage control systems and the increased heat production from the manyindividual chips needed to produce the white light's component colors.But each of the single-chip systems have their problems too, perhapsmost notably being the inability to achieve an acceptable colorrendering outcome. What is needed in the art is a white lightillumination system with enhanced luminosity and color rendering, whileat the same time achieving a balance with the need for moresophisticated drive and control systems.

Furthermore, there is a need for more power efficient illuminationsystems for Liquid Crystal Displays (LCD) that can meet the exactingindustry specifications.

SUMMARY OF THE INVENTION

Embodiments of the present invention are directed toward illuminationsystems, typically white light illumination systems, comprising amulti-chip excitation source and a phosphor package comprising a narrowband green phosphor. Typically the multi-chip excitation source is atwo-chip source comprising two LEDs; a UV to near UV-emitting LED and ablue-emitting LED for co-exciting the phosphor package.

According to further embodiments, a white light illumination system maycomprise: a phosphor package; a first radiation source for providingco-excitation radiation to the phosphor package, the source emitting inwavelengths ranging from about 250 nm to about 410 nm; and a secondradiation source for providing co-excitation radiation to the phosphorpackage, the source emitting in wavelengths ranging from about 410 nm toabout 540 nm; wherein the phosphor package is configured to emitphotoluminescence comprising light with wavelengths ranging from about440 nm to about 700 nm upon co-excitation from the first and secondradiation sources, and wherein the phosphor package comprises at leastone narrow band green phosphor with a photoluminescence peak with a fullwidth at half maximum of less than 60 nm, and wherein the narrow bandgreen phosphor is configured to emit photoluminescence in wavelengthsranging from about 500 nm to about 550 nm. Furthermore, the narrow bandgreen phosphor may have a composition given by the formulaM_(a)Eu_(1−a)Al_(b)O_(c), wherein: M is at least one divalent metalselected from the group consisting of Mg, Ca, Sr, Ba, Mn, Zn, Cu, Cd, Smand Tm; 0<a≦1.0; 0.5≦b≦12.0; and 1.75≦c≦19.0. Yet furthermore, thenarrow band green phosphor may be a BAM phosphor—for example, with acomposition given by the formula M_(1−x)Eu_(x)Mg_(1−y)Mn_(y)Al₁₀O₁₇wherein M is at least one alkaline earth metal, 0.01<x≦1.0, and0.01<y≦1.0. Furthermore, the phosphor package may further comprise atleast one phosphor selected from the group consisting of a blue emittingphosphor, a yellow-green emitting phosphor, an orange emitting phosphor,and a red emitting phosphor, including combinations thereof.

According to yet further embodiments, a white light illumination systemmay comprise: a phosphor package; a first radiation source for providingco-excitation radiation to the phosphor package, the source emitting inwavelengths ranging from about 250 nm to about 410 nm; and a secondradiation source for providing co-excitation radiation to the phosphorpackage, the source emitting in wavelengths ranging from about 410 nm toabout 540 nm; wherein the phosphor package is configured to emitphotoluminescence comprising light with wavelengths ranging from about440 nm to about 700 nm upon co-excitation from the first and secondradiation sources, and wherein the phosphor package comprises a greenphosphor with chromaticity coordinates CIE (x, y) within an area of CIE1931 xy chromaticity diagram defined by a simple quadrilateral withvertices (0.120, 0.775), (0.230, 0.755), (0.360, 0.620) and (0.150,0.650), in embodiments a simple quadrilateral with vertices (0.128,0.768), (0.205, 0.753), (0.278, 0.660) and (0.150, 0.680), and in otherembodiments a simple quadrilateral with vertices (0.135, 0.760), (0.180,0.750), (0.195, 0.700) and (0.150, 0.710). Furthermore, the phosphorpackage may further comprise a red phosphor having chromaticitycoordinates CIE (x, y) within an area of the CIE 1931 xy chromaticitydiagram defined by a simple quadrilateral with vertices (0.61, 0.39),(0.70, 0.30), (0.68, 0.30) and (0.59, 0.39).

According to further embodiments, a photoluminescence color display maycomprise: a display panel comprising a plurality of red, green and bluepixel areas; a white light illumination system; and a color filter platelocated on a side of the display panel that is distal to the white lightillumination system, wherein the color filter plate comprises at leastone of: first filter areas corresponding to red pixel areas of thedisplay that are operable to allow the passage of red light; secondfilter areas corresponding to green pixel areas of the display that areoperable to allow the passage of green light; and third filter areascorresponding to blue pixel areas of the display that are operable toallow the passage of blue light; and wherein the white lightillumination system comprises: a phosphor package; a first radiationsource for providing co-excitation radiation to the phosphor package,the source emitting in wavelengths ranging from about 250 nm to about410 nm; a second radiation source for providing co-excitation radiationto the phosphor package, the source emitting in wavelengths ranging fromabout 410 nm to about 540 nm; and wherein the phosphor package isconfigured to emit photoluminescence in wavelengths ranging from about440 nm to about 700 nm upon co-excitation from the first and secondradiation sources, and wherein the phosphor package comprises at leastone narrow band green phosphor with a photoluminescence peak with a fullwidth at half maximum of less than 60 nm, and wherein the narrow bandgreen phosphor is configured to emit photoluminescence in wavelengthsranging from about 500 nm to about 550 nm.

According to yet further embodiments, a photoluminescence color displaymay comprise: a display panel comprising a plurality of red, green andblue pixel areas; an excitation source operable to generate excitationradiation for operating the display, said excitation source comprising:a first radiation source emitting in wavelengths ranging from about 250nm to about 410 nm; and a second radiation source emitting inwavelengths ranging from about 410 nm to about 540 nm; aphotoluminescence color-elements plate comprising at least one of: afirst photoluminescence material corresponding to red pixel areas of thedisplay that is operable to emit red light in response to saidexcitation radiation; a second photoluminescence material correspondingto green pixel areas of the display that is operable to emit green lightin response to said excitation radiation; and a third photoluminescencematerial corresponding to blue pixel areas of the display that isoperable to emit blue light in response to said excitation radiation;and a color filter plate located on a side of the display panel that isdistal to the white light illumination system, wherein the color filterplate comprises at least one of: first filter areas corresponding to redpixel areas of the display that are operable to allow the passage of redlight; second filter areas corresponding to green pixel areas of thedisplay that are operable to allow the passage of green light; and thirdfilter areas corresponding to blue pixel areas of the display that areoperable to allow the passage of blue light; wherein the secondphotoluminescence material comprises at least one narrow band greenphosphor with a photoluminescence peak with a full width at half maximumof less than 60 nm, and wherein the narrow band green phosphor isconfigured to emit photoluminescence in wavelengths ranging from about500 nm to about 550 nm.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects and features of the present invention willbecome apparent to those ordinarily skilled in the art upon review ofthe following description of specific embodiments of the invention inconjunction with the accompanying figures, wherein:

FIG. 1 is a plot of emission intensity versus wavelength for a two-LEDradiation source providing excitation radiation to a two-phosphorsystem, the LEDs emitting at 402 and 454 nm, and the phosphors havingpeak emission intensities at 507 and 610 nm, respectively;

FIG. 2 is a plot of emission intensity versus wavelength for a two-LEDradiation source providing excitation radiation to a three-phosphorsystem, the LEDs emitting at 402 and 454 nm, and the phosphors havingpeak emission intensities at 507, 550, and 610 nm, respectively;

FIG. 3 is a plot of emission intensity versus wavelength for a two-LEDradiation source providing excitation radiation to a four-phosphorsystem, the LEDs emitting at 402 and 454 nm, and the phosphors havingpeak emission intensities at 450, 507, 550, and 610 nm, respectively;

FIG. 4 is a plot of emission intensity versus wavelength for a two-LEDradiation source providing excitation radiation to a three-phosphorsystem, the LEDs emitting at 402 and 454 nm, and the phosphors havingpeak emission intensities at 507 and 610 nm, respectively;

FIG. 5 is a plot of emission intensity versus wavelength for a two-LEDradiation source providing excitation radiation to a three-phosphorsystem, the LEDs emitting at 429 and 457 nm, and the phosphors havingpeak emission intensities at 507, 550, and 610 nm, respectively;

FIG. 6 is a plot of emission intensity versus wavelength for a two-LEDradiation source providing excitation radiation to a two-phosphorsystem, the LEDs emitting at 454 and 523 nm, and the phosphors havingpeak emission intensities at 530 and 590 nm, respectively;

FIG. 7 is a plot of emission intensity versus wavelength for a singleLED radiation source providing excitation radiation to a two-phosphorsystem, the LED emitting at 402 nm, and the phosphors having peakemission intensities at 538 and 586 nm, respectively;

FIG. 8 is a plot of emission intensity versus wavelength for a singleLED radiation source providing excitation radiation to a four-phosphorsystem, the LED emitting at 402 nm, and the phosphors having peakemission intensities at 450, 507, 550, and 610 nm, respectively;

FIG. 9 is a plot of emission intensity versus wavelength for a singleLED radiation source providing excitation radiation to a three-phosphorsystem, the LED emitting at 402 nm, and the phosphors having peakemission intensities at 507, 550, and 610 nm, respectively;

FIG. 10 is a plot of emission intensity versus wavelength for a singleLED radiation source providing excitation radiation to a two-phosphorsystem, the LED emitting at 429 nm, and the phosphors having peakemission intensities at 507 and 610 nm, respectively;

FIG. 11 is a representation of a white light illumination systemaccording to some embodiments of the invention;

FIG. 12 is a representation of a white light illumination systemaccording to some further embodiments of the invention;

FIG. 13 is a representation of a white light illumination systemembedded within a lens according to some further embodiments of theinvention;

FIG. 14 is a CIE 1931 xy chromaticity diagram showing the area coveredby the light emitted from an embodiment of the white light illuminationsource of the invention compared with the NTSC 1953 color gamutspecification;

FIG. 15 is a CIE 1931 xy chromaticity diagram showing areas in which thechromaticity coordinates for green phosphors and red phosphors in thephosphor package of certain embodiments of the white light illuminationsystem of the invention may be located;

FIG. 16 is a detail of the CIE 1931 xy chromaticity diagram of FIG. 15with CIE coordinates for various narrow band green phosphors accordingto embodiments of the present invention;

FIG. 17 is an emission spectrum of a narrow band green phosphoraccording to some embodiments of the invention;

FIG. 18 is the excitation spectrum of the phosphor with the emissionspectrum of FIG. 15;

FIG. 19 is a schematic cross-sectional representation of a color liquidcrystal display according to embodiments of the invention;

FIG. 20 is a schematic diagram of a unit pixel of a color filter plateof the display of FIG. 19;

FIG. 21 is a schematic cross-sectional representation of aphotoluminescence color LCD according to some further embodiments of theinvention; and

FIG. 22 is a schematic diagram of a unit pixel of a photoluminescentcolor-elements plate of the display of FIG. 21.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will now be described in detailwith reference to the drawings, which are provided as illustrativeexamples of the invention so as to enable those skilled in the art topractice the invention. Notably, the figures and examples below are notmeant to limit the scope of the present invention to a singleembodiment, but other embodiments are possible by way of interchange ofsome or all of the described or illustrated elements. Moreover, wherecertain elements of the present invention can be partially or fullyimplemented using known components, only those portions of such knowncomponents that are necessary for an understanding of the presentinvention will be described, and detailed descriptions of other portionsof such known components will be omitted so as not to obscure theinvention. In the present specification, an embodiment showing asingular component should not be considered limiting; rather, theinvention is intended to encompass other embodiments including aplurality of the same component, and vice-versa, unless explicitlystated otherwise herein. Moreover, applicants do not intend for any termin the specification or claims to be ascribed an uncommon or specialmeaning unless explicitly set forth as such. Further, the presentinvention encompasses present and future known equivalents to the knowncomponents referred to herein by way of illustration.

In one embodiment of the invention, the white LED is comprised of tworadiation sources and at least two phosphors types chosen from blue,green, yellow, orange or red. The relative intensity of the tworadiation sources can be equal, or tuned to a special ratio to optimizethe final LED performance, such as the brightness, efficiency, color andthe color rendering index (CRI).

Characterization of Light, Including White Light

One type of classification system developed to characterize the qualityof white light was developed in 1965 by the Commission Internationale del'Eclairage (CIE), and a summary of their recommendations has beenreviewed by Ducharme et al. in U.S. Pat. No. 7,387,405. The CIE adviseda measuring the color rendering properties of light sources based on asample test color method. This method has been updated and is describedin the CIE 13.3-1995 technical report titled “Method of Measuring andSpecifying Color Rendering Properties of light sources,” the disclosureof which is hereby incorporated by reference. In essence, the methodinvolves the spectroradiometric measurement of the light source beingtested. This data is multiplied by the reflectance spectrums of eightcolor sample. The resulting spectrums are then converted to tristimulusvalues based on the CIE 1931 standard observer. The shift of thesevalues with respect to a reference light are determined for the uniformcolor space (UCS) recommended in 1960 by the CIE. The average of theeight color shifts is calculated to generate the General Color RenderingIndex, known as the CRI. Within these calculations the CRI is scaled sothat a perfect score equals 100, where “perfect” means using a sourcespectrally equal to a reference source (often sunlight and/or fullspectrum light).

Artificial lighting generally uses the standard CRI to determine thequality of white light. If a white light yields a high CRI compared tosunlight and/or a full spectrum light, then it is considered to have abetter quality in that it is more “natural,” and more likely to enable acolored surface to better rendered. But in addition to providing betterquality white light, it is also highly desirable to generate specificcolors of light. Light tends to be more orange to red in the morning,and more blue in the night or evening, so the ability to change,fine-tune, or control a specific color or range of colors within thefull spectrum is also important.

As taught by Ducharme et al. in U.S. Pat. Publication 2007/0258240,white light is a mixture of different wavelengths of light, and thus itis possible to characterize it based on the component colors used togenerate it. Different colors may be combined to generate white light,including but not limited to: 1) red, green, and blue, 2) light blue,amber, and lavender, and 3) cyan, magenta, and yellow. In fact, acombination of only two colors may be combined to generate light thatstill appears white to the eye if these two chosen colors are so-calledcomplementary, and an example of this is narrow band sources (LEDs, orin the extreme case, lasers) emitting around 635 nm and 493 nanometers.These artificial whites may appear white to the human eye, but in otherways inferior to full spectrum light and/or natural sunlight in thatthey will appear artificial when shown on a colored surface. The reasonthis happens is the colored surface under examination absorbs andreflects wavelength regions differentially. If such a surface is hit byfull spectrum white light or natural sunlight, which means light havingcomponent wavelengths in the visible band fully represented atreasonable and/or desired intensities, the surface will absorb andreflect perfectly. But the artificial white lights described in thisparagraph having only two or three components do not contain thecomplete spectrum. To give an example of what different color renderingmeans in two different situations: a surface that reflects in the 500 to550 nm range will appear deep-green under full spectrum light, but blackunder the hypothetical “white light” generated by the hypothetical twocomponent system comprising two narrow band sources emitting at around635 nm and 493 nanometers.

Optical Results

The optical results to be discussed in this section will be quantifiedby way of graphs that plot emission intensity of the system as afunction of spectral wavelength. It is, in fact, convenient to startwith the spectrum of a conventional blue LED plus yellow YAG:Cephosphor, as exemplified by Chen et al. in U.S. Pat. Publication2008/0203900. Their FIG. 1 shows that the spectrum is deficient in redbut especially so in the green. They suggest adding LEDs that preferablyemit light in the blue-green region of the spectrum; i.e. 480 to 500 nm,and in the amber-red region of the spectrum; i.e. 580 to 680 nm. TheirFIG. 2 shows a spectrum that is obtained by adding a blue-green LEDhaving a center wavelength of approximately 500 nm to the white lightsystem whose elimination was shown in their FIG. 1.

The addition of this LED by Chen et al. produces a spectrum that issubstantially more constant in luminosity as a function of wavelengththan that of the two component blue LED and yellow phosphor (e.g.YAG:Ce) system. The spectrum from a three LED—one phosphor system isshown in their FIG. 3, where a third LED emitting from 580 to 680 nm hasbeen added to the system. The intensity of this spectrum over a range450 to 650 nm is substantially more constant than the single LED/singlephosphor (e.g., blue LED/YAG:Ce yellow phosphor) or two componentversion of a white LED. The power in the second, blue-green LED and/orthird, orange-red LED is a small fraction of the power in the first blueLED that provides blue light as well as excitation radiation to theyellow phosphor, and thus the overall efficiency of the system has onlybeen slightly reduced, yet the overall color rendering ability of thethree component system has been enhanced. Thus multiple LEDs have beenshown to be effective from an overall efficiency point of view.

Though LEDs in addition to the traditional blue LED have been used inwhite light illumination systems, these supplementary LEDs are used toprovide a component of light to the final white light product, and (tothe inventors knowledge) not to provide an additional source ofexcitation radiation. The term “co-excitation” as used herein will meanthat at least two different LEDs provide a combined excitation radiationcovering two different wavelengths or wavelength ranges to a phosphorand/or phosphor mixture (also called phosphor package), which mayinclude two or more phosphors. The at least two LEDs each providesexcitation radiation to the phosphor package, and may include acombination of any of a UV or near-UV LED and a blue, green, or yellowLED, and even an orange LED if it is configured to excite a redphosphor. In fact, that is a principle of the embodiments of the presentinvention: an LED may be used to excite any phosphor whose excitationenergy is equal to or less than the bandgap energy of the LED inquestion, or stated more generally, an LED emitting at a certainwavelength may excite a phosphor whose luminescence is at a wavelengthlower in energy than that of the LED's emission. So a green LED, forexample, may be used to excite a yellow phosphor, or perhaps moreefficiently, an orange or red phosphor, this event happening inconjunction with the conventional blue LED exciting a yellow phosphor(and possibly also a green, orange or red phosphor, etc.).

The first three examples of the present embodiments are directed to asystem comprising two excitation LEDs: the first radiation sourceemitting excitation radiation to a phosphor package in wavelengthranging from about 250 to 410 nm, and thus it might be considered a UVto near-UV LED, and a second radiation source in emitting light in awavelength ranging from 410 to 480 nm, and so this excitation source issubstantially the same as the conventional blue LED used in blueLED/yellow phosphor systems. The phosphor mixtures tested with thistwo-LED excitation configuration are built up in the following manner:in the first example the phosphor package is a green and an orangephosphor, in the second example it is a green, yellow, and orangephosphor, and in the third example it is a blue, green, yellow, andorange phosphor. The members of this phosphor package each emit in the440 to 700 nm wavelength range. The innovative concept in thisembodiment is the use of a UV excitation LED in addition to theconventional blue LED, both LEDs simultaneously providing excitationradiation to the phosphors. With regards to the phosphor package towhich the UV and blue LED sources are providing excitation radiation, awide variety of choices are available. But some phosphors, such assilicate-based phosphor having high quantum efficiency as the excitationwavelength decreases from 470 to 250 nm as taught by the inventors ofthe present disclosure, result in an enhanced luminosity (brightness)achieved via the UV light source. Another advantage of using UV lightsource is that a phosphor with a shorter emission wavelength may be usedto effectively absorb the UV light rather than the blue light from theexcitation sources, such that the luminescence spectrum of the finalproduct may cover a broader range of wavelengths, thus increasing theCRI value.

The results of the UV and blue LED excitation chips used in conjunctionwith a green phosphor designated G507 and an orange phosphor designatedO610 are shown in FIG. 1. More will be said about the phosphors,particularly their compositions, later in this disclosure, but for nowit will be noted that in this nomenclature, the letter is the color, andthe number represents the wavelength at peak emission for thatparticular phosphor. The relative ratio of two phosphors was chosen toachieve a target CIE having x, y values close to (0.3, 0.3). So thatother chip combinations and phosphor mixtures may be compared in ameaningful manner, the same CIE targets were chosen for the remainingnine examples. Thus brightness and CRI may be directly compared. In thisfirst example the brightness was 31.32, and the CRI was 91.8, whichshows immediately that color renderings over 90 CRI may be achieved withthe present embodiments.

In the second example a yellow phosphor designated Y550 was added to thegreen and orange mix (G507 and O610, respectively) discussed previouslyin the first example. FIG. 2 shows the emission spectrum from a whiteLED utilizing the same UV and blue LED chip sources from the firstexample (402 nm and 454 nm). This time blue/UV LEDs co-exciting ayellow, green, and orange phosphor package produced white lightillumination with more than a 30% increase in brightness. This increasein brightness was achieved via the addition of the yellow phosphor, assubstantially all the other variables of the experiments were heldconstant. The white light produced in this second example may becharacterized as having a brightness of 40.64, and a CRI of 80.7.

Unlike the first example that involved a mixture of two phosphors, inthis second embodiment with a three-phosphor mixture in the phosphorpackage, there is created an essentially infinite number of blendingratios that can achieve the same target CIE. Generally, the addition ofa yellow phosphor provided the advantage on high brightness, while thegreen and orange phosphors work advantageously to increase the CRI. Inother words, optimization of the CRI value and the brightness may beachieved separately by fine tuning the ratio of the yellow phosphorconcentration to that of the orange and green phosphors.

In the third example, a blue phosphor designated B450 was added to thegreen, yellow, and orange mix (G507, Y550, O610, respectively) discussedin the second example. FIG. 3 shows the emission spectrum from a whiteLED utilizing the same UV and blue LED chip sources as in the first andsecond examples (402 nm and 454 nm). The brightness was 23.62, the CRI89.1. The blue phosphor effectively absorbs the UV light from thismulti-chip excitation source, while being substantially transparent tothe blue light from the blue LED, allowing it to co-excite the yellow,green, and orange phosphors in the system. It should be noted that theblue phosphor used in this particular test demonstrated less than 50%quantum efficiency at the 402 nm excitation wavelength, and it iscontemplated that a greater than 30% increase in brightness may beachieved with blue phosphors that have a 70% quantum efficiency.

In the fourth and fifth examples of the present embodiments, a differentchip set was used. Here, the two chips provided co-excitation radiationat wavelengths centered at 429 and 457 nm, respectively. These areexamples of a two-chip co-excitation source where the first radiationsource emits light in a wavelength ranging from 410 to 440 nm, and wherethe second radiation source emits light at wavelengths ranging from 440to 480. So whereas the chip set in the first three examples might bedescribed as a UV and blue combination, the chip set in the fourth andfifth examples are a purple (could also be described as violet) LED andblue LED set. The purple LED emits at 429 nm, which is just at theshortest end of the spectrum where the human eye is able to detectillumination. The other LED is a blue LED which emits at 457 nm,substantially the same as that used in the conventional white LED (blueLED/YAG:Ce). The blue and purple multi-chip set was used to provideco-excitation radiation to two different phosphor packages, as describedbelow.

In the fourth example the phosphor package contained two phosphors, onegreen and one orange (G507, and O610, respectively). The two phosphorsin this package photoluminesce at wavelengths ranging from 480 to 700nm. The 410 to 440 nm radiation will contribute light itself to finalwhite light illumination product, and thus determine at least in partthe color and brightness of the white light, in contrast to the chip setcontaining the UV LED. On the other hand, it demonstrates a greaterefficiency in exciting yellow and green phosphors, so the majoradvantage of such a combination is to allow the use of shorter emissionwavelength phosphors in order to achieve high CRI value whilemaintaining brightness.

A spectrum of the white light illumination from this system is shown inFIG. 4. The brightness of the illumination was 38.37, and the CRI was92.0.

In the fifth example a yellow phosphor designated Y550 was added to thegreen and orange mix (G507 and O610, respectively) discussed previouslyin the fourth example. FIG. 5 shows the emission spectrum from a whiteLED utilizing the same purple and blue LED chip radiation sources fromthe first example (429 nm and 457 nm, respectively, representingradiation sources of 410 to 440 nm, and 440 to 480 nm sources,respectively). This time the purple/blue LEDs co-exciting a yellow,green, and orange phosphor package produced white light illuminationwith more than a 30% increase in brightness. As in the transition fromthe second to third examples, this increase in brightness from thefourth to fifth examples was achieved via the addition of the yellowphosphor, as substantially all the other variables of the experimentswere held constant, and optimization of the CRI value and the brightnessmay be achieved separately by fine tuning the ratio of the yellowphosphor concentration to that of the orange and green phosphors. Thewhite light produced in this second example may be characterized ashaving a brightness of 52.0, and a CRI of 79.9.

The multi-chip excitation source in the first five examples was either aUV/blue combination or a purple/blue combination. High brightness, highCRI white light illumination sources can be provided by using a bluechip and green chip with a phosphor package having two phosphors in oneembodiment, and three phosphors in another. These phosphors can be anycombination of a green phosphor such as G530, a yellow phosphor such asY550), an orange phosphor such as O590, and a red phosphor such as R662.In this sixth example, the chip set was a blue LED in combination with agreen LED. So in example three the white LED comprised a first radiationsource emitting light in wavelength ranging from 440 to 480 nm, and asecond radiation source co-exciting a phosphor package, the secondradiation source emitting light in wavelengths ranging from 480 to 540nm. This chip set provided co-excitation radiation to at least two typesof phosphors emitting light in wavelength range from 500 to 700 nm. Morespecifically, the mixed phosphors in the system exemplified by the sixthembodiment contained a green and orange phosphor (G530 and O590), wherean orange or red phosphor is included because of the 480 to 540 nmemitting blue-green LED. Some orange and red phosphors, such assilicate-based phosphors, have a higher quantum efficiency as theexcitation wavelength increases from 440 to 550 nm, so the use of greenexcitation radiation increases the efficiency of an orange and/or redphosphor so as to achieve higher brightness. The further addition ofother green and/or yellow phosphor can broaden the final LED emissionwavelength spectrum, thus increase the CRI value.

FIG. 6 shows a white LED made from a chip set comprising a 454 nm LEDand a 523 nm LED, this chip set providing co-excitation radiation to aphosphor package comprising a 530 nm green phosphor and a 590 nm orangephosphor. The brightness was 43.92, and the CRI value 71.9; again, thebrightness and/or CRI values may be optimized by using differentphosphors, and by tuning the respective intensities of the green versusblue LEDs.

Table 1 summarizes the testing results of the white light illuminationsystems of FIGS. 1-6, where the CIE coordinates have been substantiallyfixed at x and y values of 0.3 and 0.3 respectively, and where the whitelight is characterized by brightness and CRI values.

TABLE 1 Brightness Phosphor LED CIE x CIE y (a.u.) CRI G507 + O610 402nm + 454 nm 0.286 0.304 31.32 91.8 G507 + Y550 + 402 nm + 454 nm 0.3030.300 40.64 80.7 O610 B450 + G507 + 402 nm + 454 nm 0.307 0.294 23.6289.1 Y550 + O610 G507 + O610 429 nm + 457 nm 0.302 0.302 38.37 92.0G507 + Y550 + 429 nm + 457 nm 0.309 0.293 52.07 79.9 O610 G530 + O590454 nm + 523 nm 0.295 0.301 43.92 71.9

For comparison to these multi-chip systems, a similar set of experimentswas carried out with a single-chip excitation source. The LEDs in thesesingle-chip examples emitted excitation radiation in a wavelengthranging from 250 nm to 440 nm; they were in the seventh through tenthexamples: 402, 402, 417, and 429 nm, respectively. The phosphor packageswere different combinations of blue, green and orange phosphors.Specifically they were blue, green, and orange in the seventh example;blue, green, yellow, and orange in the eighth example; green, yellow,and orange in the ninth example, and green and orange in the tenthexample.

FIG. 7 shows the emission spectrum from a white LED made constructedusing from a 402 nm LED, a 450 nm blue phosphor, a 538 nm blue-greenphosphor, and a 586 nm orange phosphor. The blue phosphor used in hadless than a 50% quantum efficiency at the 402 nm excitation wavelength,and more than a 30% increase in brightness could be achieved with a bluephosphor having a 70% quantum efficiency. The brightness was 10.63; theCRI 64.7.

FIG. 8 shows the emission spectrum from a white LED constructed from a402 nm LED, a 450 nm blue phosphor, a 507 nm blue-green phosphor, a 550nm yellow phosphor, and a 610 nm orange phosphor. The brightness was8.29 and the CRI was 91.7.

FIG. 9 shows the emission spectrum from a white LED made constructedfrom a 417 nm LED, a 507 nm blue-green phosphor, a 550 nm yellowphosphor and a 610 nm orange phosphor. The brightness was 14.53 and theCRI was 62.8.

FIG. 10 shows the emission spectrum from a white LED made constructedfrom a 429 nm LED, a 507 nm blue-green phosphor, and a 610 nm orangephosphor. The brightness was 23.98, and the CRI was 86.8.

Table 2 summarizes the testing results of the white light illuminationsystems of FIGS. 7-10, where the CIE coordinates have been substantiallyfixed at x and y values of 0.3 and 0.3 respectively, and where the whitelight is characterized by brightness and CRI values.

TABLE 2 Brightness Phosphor LED CIE x CIE y (a.u.) CRI B450 + G538 +O586 402 nm 0.304 0.335 10.63 64.7 B450 + G507 + Y550 + O610 402 nm0.301 0.298 8.29 91.7 G507 + Y550 + O610 417 nm 0.296 0.301 14.53 62.8G507 + O610 429 nm 0.275 0.312 23.98 86.8

In yet another embodiment of the present invention, a white LEDcomprises a first radiation source emitting excitation radiation in awavelength ranging from about 250 nm to about 440 nm, a second radiationsource emitting excitation radiation in a wavelength ranging from about440 nm to about 480 nm, and a phosphor package comprising anyellow-orange phosphor having a peak emission wavelength ranging fromabout 540 to 600 nm, and/or a red phosphor having a peak emissionwavelength ranging from about 580 to about 780 nm.

Exemplary Phosphor Compositions

The advantages of the present multi-chip excitation sources are notrestricted to any particular type of phosphor. Indeed, it iscontemplated that virtually any of the commercial blue, green, yellow,orange, and red phosphors listed in Section 8 and Appendix II ofInorganic Phosphors, by William M. Yen and Marvin J. Weber (CRC Press,New York, 2004). Section 8 and Appendix II of this reference istherefore incorporated herein by reference in their entirety.

Examples of the blue, blue-green, yellow, yellow-orange, orange, and redphosphors that are suitable to carry out the teachings of the presentembodiments include the aluminates, silicates, and nitrides (andmixtures thereof) that have been developed by the present inventors.Although the present embodiments are not restricted to the followingdefinitions, it is true that for the examples in the disclosure the bluephosphors tended to be aluminate-based; the green phosphors could beeither aluminates or silicates, the yellow and orange phosphors tendedto be silicate-based, albeit with different types of host structures;and the red phosphors are nitrides.

An exemplary blue aluminate-based phosphor has the general formula(M_(1−x)Eu_(x))_(2−z)Mg_(z)Al_(y)O_([2+(3/2)y]), where M is a divalentalkaline earth metal other than magnesium (Mg) from group IIA of theperiodic table, where 0.05<x<0.5; 3≦y≦12; and 0.8≦y≦1.2. The compositionmay contain a halogen dopant, such as fluorine or chlorine. M may beeither Ba (barium) or Sr (strontium); when M is Ba, the phosphor is amember of the present barium aluminate magnesium (BAM) series; when M isstrontium, the phosphor is a member of the present strontium magnesiumaluminate (SAM) series. The halogen dopant may reside on oxygen latticesites within the crystalline lattice host, and is present in an amountranging from about 0.01 to 20 mole percent. The phosphor in this exampleis configured to absorb radiation in a wavelength ranging from about 280nm to about 420 nm, and to emit visible light having a wavelengthranging from about 420 nm to 560 nm.

An exemplary phospho-chloride that may be used as the blue phosphor inthe present embodiments, and the phosphor B450 that was used to generatethe data in FIGS. 3, 7, and 8 has the formula Sr₅Cl(PO₄)₃:Eu,specifically Sr₁₀(PO₄)₆Cl₂Eu_(0.05).

It is reiterated that the types of phosphors or the specific phosphorsare not the key to the embodiments of the present invention; rather, itis that the at least two LEDs in the system are there substantially toprovide excitation radiation to the at least one phosphor in thephosphor package, and not to provide light to the final illuminationproduct. Thus it is contemplated that virtually any phosphor(s) willwork, and this includes commercially available phosphors. Commerciallyavailable blue phosphors that may be used according to the presentembodiments include (CeMg)SrAl₁₁O₁₈:Ce, (CeMg)BaAl₁₁O₁₈:Ce, YAlO₃:Ce³⁺,Ca₂MgSi₂O₇:Ce³⁺, Y₂SiO₅:Ce³⁺, Zn₂SiO₄:Ti, CsI:Na⁺, Sr₂P₂O₇:Eu,Sr₅Cl(PO₄)₃:Eu, BaMgAl₁₀O₁₇:Eu,Mn (BAM), and ZnS:Ag,Cl,Ni. Thesephosphors emit at wavelengths up to about 460 nm.

The green phosphors may be either aluminate or silicate-based, or acombination of both. The aluminate-based green phosphors may berepresented by the general formula M_(1−x)Eu_(x)Al_(y)O_([1+3y/2]),where M is at least one of a divalent metal selected from the groupconsisting of Ba, Sr, Ca, Mg, Mn, Zu, Cu, Cd, Sm, and Tm; 0.1<x<0.9; and0.5≦y≦12. These aluminate-based green phosphors are configured to absorbsubstantially non-visible radiation having a wavelength ranging fromabout 280 to 420 nm, and emit visible green light having a wavelengthranging from about 500 to 550 nm. In a particular embodiment, thephosphor contains the divalent alkaline earth metals Mg, and Mn may bepresent as well.

The silicate-based green phosphors appropriate for the present whiteLEDs using multi-chip co-excitation sources have the general formula(Sr,A₁)_(x)(Si,A₂)(O,A₃)_(2+x):Eu²⁺, where A₁ is at least one of adivalent 2+ alkaline earth or transition metal cation selected from thegroup consisting of Mg, Ca, Ba, and Zn, wherein the stoichiometricamount of A₁ varies from 0.3 to 0.8, both inclusive; A₂ is P, B, Al, Ga,C, and Ge; and A₃ is a anion including a halogen selected from the groupconsisting of F and Cl, but also included are Br, C, N, and S. Theformula is written to indicate that the A₁ cation replaces Sr; the A₂cation replaces Si, and the A₃ anion replaces O. The amounts of A₂ andA₃ each range from 0 to 19 mole percent, both endpoints inclusive; and xis any value between 1.5 and 2.5. A₁ could also include a combination of1+ and 3+ cations, the 1+ cations including Na, K, and Li, and the 3+cations including Y, Ce, and La.

Exemplary silicates that may be used as the green phosphors in thepresent embodiments and designated G507 in FIGS. 1-5 and 8-10 has theformula Ba_(1.96)Mg_(0.04)Eu_(0.06)Si_(1.03)O₄Cl_(0.12). The phosphordesignated G530 in FIG. 6 has the formulaSr_(1.03)Ba_(0.92)Mg_(0.05)Eu_(0.06)Si_(1.03)O₄Cl_(0.12). The phosphordesignated G538 in FIG. 7 has the formulaSr_(1.15)Ba_(0.80)Mg_(0.05)Eu_(0.06)Si_(1.03)O₄Cl_(0.12). Anotherformula for an appropriate silicate-based green phosphor (not shown inthe figures) isG525:Sr_(0.925)Ba_(1.025)Mg_(0.05)Eu_(0.06)Si_(1.03)O₄Cl_(0.12).

Commercially available green phosphors that may be used according to thepresent embodiments include Bi₄Ge₃O₁₂, Ca₅(PO₄)₃F:Sb, (Ba,Ti)₂P₂O₇:Ti,Sr₅(PO₄)₃F:Sb,Mn, ZnO:Zn, ZnS:Cu,Cl, Zn₂SiO₄:Mn²⁺, and Y₃Al₅O₁₂:Ce³⁺.These phosphors emit at wavelengths roughly between about 480 and 530nm, and the designation of this range as being “green,” as opposed to“blue-green” or “yellow-green” is arbitrary and not particularlyimportant.

An exemplary silicate-based yellow-green phosphor has the generalformula A₂SiO₄:Eu²⁺D, wherein A is at least one of a divalent metalselected from the group consisting of Sr, Ca, Ba, Mg, Zn, and Cd; and Dis a dopant selected from the group consisting of F, Cl, Br, I, P, S andN. The dopant D is present in the phosphor in an amount ranging fromzero to about 20 mole percent. In another embodiment, the phosphor hasthe formula (Sr_(1−x−y)Ba_(x)M_(y))₂SiO₄:Eu²⁺F, Cl, where M is one ofCa, Mg, Zn, or Cd in an amount ranging from 0<y<0.5.

An exemplary silicate that may be used as the yellow phosphor in thepresent embodiments, and the phosphor Y550 that was used to generate thedata in FIGS. 2, 3, 5, 8, and 9 has the formulaSr_(1.34)Ba_(0.61)Mg_(0.05)Eu_(0.06)Si_(1.03)O₄Cl_(0.12). A YAG:Ce³⁺phosphor may also be used to provide the yellow component. Anothersilicate-based phosphor (not shown in the figures) has the designationEY4453 and formulaSr_(1.46)Ba_(0.45)Mg_(0.05)Eu_(0.1)Si_(1.03)O₄Cl_(0.18).

Commercially available yellow phosphors that may be used according tothe present embodiments include ZnS:Pb,Cu, ZnS:Ag,Cu,Cl, Y₃Al₅O₁₂:Tb³⁺,(Ce,Tb)MgAl₁₁O₁₉:Ce,Tb, Y₃Al₅O₁₂:Ce³⁺, MgF₂:Mn²⁺, CsI:Tl, and(Zn,Mg)F₂:Mn²⁺. These phosphors emit at wavelengths roughly betweenabout 530 and 590 nm, and the designation of this range as being“yellow,” as opposed to “yellow-green” or “yellow-orange” is arbitraryand not particularly important.

Silicate-based orange phosphors appropriate for the present multi-chipwhite LEDs have the general formula (Sr,A₁)_(x)(Si,A₂)(O,A₃)_(2+x):Eu²⁺,where A₁ is at least one divalent cation (a 2+ ion) including Mg, Ca,and Ba, or a combination of 1+ and 3+ cations, where 1+ cations includeNa, K, and Li, and the 3+ cations include Y, Ce, and La; A₂ is a 3+, 4+,or 5+ cation, including at least one of B, Al, Ga, C, Ge, P; A₃ is a 1−,2−, or 3− anion, including F, Cl, and Br as 1− anions; and x is anyvalue between 2.5 and 3.5, inclusive. Again, the formula is written toindicate that the A₁ cation replaces Sr; the A₂ cation replaces Si, andthe A₃ anion replaces O. A₁ varies stoichiometrically from 0.3 to 0.8,both inclusive, and the amounts of A₂ and A₃ each range from 0 to 19mole percent, both endpoints inclusive. In another embodiment, thesilicate-based orange phosphors have the formula(Sr_(1−x)M_(x))_(y)Eu_(z)SiO₅, wherein M is at least one of a divalentmetal selected from the group consisting of Ba, Mg, Ca, and Zn; 0≦x≦0.5;2.6≦y≦3.3; and 0.001≦z≦0.5. These phosphors too may contain halogendopants such as F and Cl. These orange phosphors may be excited by anyof the LED sources emitting in the UV, blue, green, and/or yellowregions of the spectrum.

Exemplary silicates that may be used as the orange phosphor in thepresent embodiments and designated O590 in FIG. 6 has the formulaBa_(0.02)Sr_(2.94)Eu_(0.1)Si_(1.02)O₅F_(0.2). The orange silicatedesignated O610 in FIGS. 1-5 and 8-10 has the formula(Sr_(0.87)Ba_(0.1)Y_(0.0167))₃Eu_(0.1)Si_(0.97)Al_(0.05)O₅F_(0.2).Another silicate-based orange phosphor that is appropriate in thepresent multi-chip co-excitation embodiments (not shown in the figures)has the designation O586 and the formulaSr₃Eu_(0.06)Si_(1.02)O₅F_(0.18).

Commercially available orange phosphors that may be used according tothe present embodiments include (Y,Gd)BO₃:Eu³⁺, Y(P,V)O₄:Eu³⁺,(Zn,Mg)F₂:Mn²⁺, (Ca,Zn,Mg)₃(PO₄)₂:Sn, CaSiO₃:Mn²⁺,Pb, Y₂O₃:Eu³⁺, andYVO₄:Eu³⁺. These phosphors emit at wavelengths roughly between about 590and 620 nm, and the designation of this range as being “orange,” asopposed to “yellow-orange” or “orange-red” is arbitrary and notparticularly important.

Red phosphors that may be used according to the present embodimentstypically have nitride-based hosts. A general formula that may be usedto describe such nitride-based red phosphor isM_(m)M_(a)M_(b)(N,D)_(n):Z_(z), where M_(m) is a divalent element; M_(a)is a trivalent element; M_(b) is a tetravalent element; N is nitrogen; Zis an activator; and D is a halogen; and where the stoichiometry of theconstituent elements (m+z):a:b:n is about 1:1:1:3, and the phosphor isconfigured to emit visible light having a peak emission wavelengthgreater than about 640 nm. Another formula that may be used to describethe present nitride-based red phosphor isM_(m)M_(a)M_(b)D_(3w)N_([(2/3)m+z+a+(4/3)b−w])Z_(z), where M_(m) is adivalent element selected from the group consisting of Be, Mg, Ca, Sr,Ba, Zn, Cd, and Hg; M_(a) is a trivalent element selected from the groupconsisting of B, Al, Ga, In, Y, Sc, P, As, La, Sm, Sb, and Bi; M_(b) isa tetravalent element selected from the group consisting of C, Si, Ge,Sn, Ni, Hf, Mo, W, Cr, Pb, Ti, and Zr; D is a halogen selected from thegroup consisting of F, Cl, Br, and I; Z is an activator selected fromthe group consisting of Eu, Ce, Mn, Tb, and Sm; N is nitrogen. Theamounts of the constituent elements may be described by the followingparameters: 0.01≦m≦1.5; 0.01≦a≦1.5; 0.01≦b≦1.5; 0.0001≦w≦0.6, and0.0001≦z≦0.5.

In an alternative embodiment, the nitride-based red phosphors have theformula M_(a)M_(b)M_(c)(N,D)_(n):E_(z), where M_(a) is not just a singledivalent element, but rather a combination of two or more divalentelements (or two divalent elements used simultaneously). The twodivalent metals may be, for example, Ca and Sr. Examples of suchphosphors are Ca_(0.98−x)Sr_(x)AlSiN₃Eu_(0.02),Ca_(0.98−x)Sr_(x)AlSiN₃Eu_(0.02), Ca_(0.98−x)Sr_(x)AlSiN₃Eu_(0.02) andCa_(0.98−x)Sr_(x)AlSiN₃Eu_(0.02), where x ranges from 0 to 0.98. Anitride-based red phosphor that is appropriate for use in the presentmulti-chip co-excitation embodiments (the red phosphor not shown in thefigures) has the designation R662 and the formulaCa_(0.97)AlSiN₃Eu_(0.0)Cl_(0.1).

Commercially available red phosphors that may be used according to thepresent embodiments include (Sr,Mg)₃(PO₄)₂:Sn, (Sr,Mg)₃(PO₄)₂:Sn,Zn_(0.4)Cd_(0.6)S:Ag, Zn₃(PO₄)₂:Mn²⁺, MgSiO₃:Mn²⁺, andMg₄(F)(Ge,Sn)O₆:Mn²⁺. These phosphors emit at wavelengths roughlygreater than about 620 nm.

LED Chips Providing Co-Excitation

The LED chips that provide the excitation radiation to the phosphorpackage in the present embodiments are in some cases based on indiumgallium nitride, with various In to Ga ratio (In_(x)Ga_(1−x)N), xvarying from about 0.02 to about 0.4 for the blue emitting chips, and xgreater than about 0.4 for the green emitting chips. The value of xseparating the blue emitting chips from the green emitting chips issomewhat arbitrary; it is the actual emission wavelength that isimportant and not the description of its color (which may besubjective). But it will be understood that higher values of xcorrespond to longer wavelengths of excitation. Blue LED chips may alsobe based on zinc selenide (ZnSe). Green emitting LED chips may be any ofthe materials gallium phosphide (GaP), aluminium gallium indiumphosphide (AlGaInP), and aluminium gallium phosphide (AlGaP). Greenemitting chips may be mixtures of InGaN and GaN. UV to near UV emittingLED chips may be of any of the materials boron nitride (BN), aluminumnitride (AlN), aluminum gallium nitride (AlGaN) and aluminum galliumindium nitride (AlGaIN).

White Light Illumination System

FIGS. 11 through 13 provide schematic representations of white lightillumination systems 106 according to some embodiments of the invention,where the white light illumination system may comprise a phosphorpackage 31, 32; a first radiation source 21 for providing co-excitationradiation to the phosphor package, the source emitting in wavelengthsranging from about 250 nm to about 410 nm; a second radiation source 22for providing co-excitation radiation to the phosphor package, thesource emitting in wavelengths ranging from about 410 nm to about 540nm; and wherein the phosphor package is configured to emitphotoluminescence in wavelengths ranging from about 440 nm to about 700nm upon co-excitation from the first and second radiation sources. Thefirst and second radiation sources may be mounted on a substrate 10, andin embodiments the first radiation source and the second radiationsource are part of a multi-chip excitation source.

Furthermore, in embodiments the first radiation source may emit inwavelengths ranging from about 390 nm to about 410 nm, and inembodiments the second radiation source may emit in wavelengths rangingfrom about 445 nm to about 455 nm. In some embodiments, the phosphorpackage may be encapsulated with the first radiation source and thesecond radiation source, and in other embodiments the phosphor packagemay be remote from the first radiation source and the second radiationsource.

In some embodiments the white light illumination system may comprise ared light source 40, which as shown in FIG. 11 is incorporated withinthe dome-shaped (e.g. hemispherical shell) phosphor package 31;alternatively, in embodiments a red light source may be separate from aUV and blue multiple excitation light source, in which case the multipleexcitation light source may provide green and blue light emission. Inthe example of FIG. 11, the phosphor package comprises at least a narrowband green phosphor, whereas in the examples of FIGS. 12 & 13 thephosphor package comprises at least a narrow band green phosphor and ared phosphor. In the examples of FIGS. 11-13 the phosphor generatedlight 50 is shown to be green for phosphor package 31, and green and redfor phosphor package 32, and light from blue and red light sources 22 &40 is shown to be transmitted through phosphor package 31 and light fromblue source 22 is shown to be transmitted through phosphor package 32.

The phosphor package 31 is shown as a dome-shaped structure (e.g.hemispherical shell) over the light sources 21, 22 and 40 in FIG. 11 andphosphor package 32 is shown as a dome-shaped (e.g. hemispherical shell)structure over the light sources 21 and 22 in FIGS. 12 & 13—keeping thephosphor package separated from the light sources may assist in avoidingsaturation of the photoluminescent emission from the narrow band greenphosphor. FIG. 13 includes a representation of a lens 60 over thephosphor package 32 which assists in uniformly distributing the emittedlight over a large solid angle—the lens 60 has a roughly torroidalshape. The phosphor package 32 may be coated over a hemispherical recessin the lens.

In embodiments, the white light illumination system may be a displaybacklighting system as described in further detail below.

Furthermore, in some embodiments a final light product generated by thewhite light illumination system may comprise photoluminescence from thephosphor package and light generated by the second radiation source, butnot light generated by the first radiation source, as described herein.A first portion of the light from the second radiation source may beabsorbed by the phosphor package to generate phosphor photoluminescenceand a second portion of the light may be transmitted through thephosphor package and contribute to the light emitted from the whitelight illumination system 106.

CIE Chromaticity Characteristics of the White Light Illumination System

According to aspects of the present invention, a white lightillumination system may comprise: a phosphor package; a first radiationsource for providing co-excitation radiation to the phosphor package,the source emitting in wavelengths ranging from about 250 nm to about410 nm; and a second radiation source for providing co-excitationradiation to the phosphor package, the source emitting in wavelengthsranging from about 410 nm to about 540 nm; wherein the phosphor packageis configured to emit photoluminescence in wavelengths ranging fromabout 440 nm to about 700 nm upon co-excitation from the first andsecond radiation sources, and wherein the phosphor package comprises agreen phosphor configured to emit photoluminescence in wavelengthsranging from about 500 nm to about 550 nm and a red phosphor configuredto emit photoluminescence in wavelengths ranging from about 600 nm toabout 700 nm, and furthermore, where the CIE chromaticitycharacteristics of the white light emitted by the system is as describedbelow with reference to FIGS. 14 and 15.

FIG. 14 is a CIE 1931 xy chromaticity diagram showing the area coveredby the light emitted from an embodiment of the white light illuminationsource of the invention compared with the NTSC (National TelevisionSystem Committee) 1953 color gamut specification. The area 1440 coveredby the light emitted from an embodiment of the white light illuminationsource of the invention is greater than 100% of the area 1430 of theNTSC 1953 color gamut 1430. In this particular example the white lightillumination system is modeled on the combination of a narrow band greenphosphor with composition given by the formulaEu_(0.4)Ba_(0.6)Mn_(0.4)Mg_(0.6)Al₁₀O₁₇, a red phosphor with compositiongiven by the formula Eu:(Sr_(0.8)Ca_(0.2))SiAlN₃ plus bromine, asdescribed in U.S. Pat. No. 8,274,215, a 400 nm LED and a 450 nm LED. Infurther embodiments, the white light illumination emitted by the systemcovers an area including greater than 90% of NTSC 1953 color gamutspecification as mapped on CIE 1931 xy chromaticity diagram.Furthermore, in embodiments the red phosphor may be a phosphor selectedfrom the phosphors described in U.S. Pat. Appl. Pub. Nos. 2013/0168605and 2013/0234589 and U.S. patent application Ser. No. 13/922,231, allincorporated by reference herein in their entirety.

FIG. 15 is a CIE 1931 xy chromaticity diagram showing areas in which thechromaticity coordinates for green phosphors and red phosphors in thephosphor package of certain embodiments of the white light illuminationsystem of the invention may be located. The green phosphor is desired tohave chromaticity coordinates CIE (x, y) within an area of CIE 1931 xychromaticity diagram defined by a simple quadrilateral 1410 withvertices (0.120, 0.775), (0.230, 0.755), (0.360, 0.620) and (0.150,0.650), in embodiments a simple quadrilateral 1412 with vertices (0.128,0.768), (0.205, 0.753), (0.278, 0.660) and (0.150, 0.680), and in otherembodiments a simple quadrilateral 1414 with vertices (0.135, 0.760),(0.180, 0.750), (0.195, 0.700) and (0.150, 0.710). The red phosphor isdesired to have chromaticity coordinates CIE (x, y) within an area ofCIE 1931 xy chromaticity diagram defined by a simple quadrilateral 1420with vertices (0.61, 0.39), (0.70, 0.30), (0.68, 0.30) and (0.59, 0.39).An example of a red phosphor falling within the quadrilateral 1420 isthe red phosphor with composition given by the formulaEu:(Sr_(0.8)Ca_(0.2))SiAlN₃ plus bromine, as described in U.S. Pat. No.8,274,215, having CIE xy chromaticity coordinates of approximately(0.67, 0.33).

FIG. 16 shows a detail of FIG. 15 including the simple quadrilaterals1410, 1412 and 1414 and the CIE coordinates of the narrow band greenphosphor materials of Table 3—see below. Note that the CIE coordinatesfor the narrow band green phosphor materials of Table 3 fall withinsimple quadrilateral 1420.

Narrow Band Green Phosphor

The white light illumination system may include a green phosphor havinga composition given by the formula M_(a)Eu_(1−a)Al_(b)O_(c), wherein: Mis at least one divalent metal selected from the group consisting of Mg,Ca, Sr, Ba, Mn, Zn, Cu, Cd, Sm and Tm; 0<a≦1.0; 0.5≦b≦12.0; and1.75≦c≦19.0. Further details of this family of phosphors, includingfabrication methods, may be found in U.S. Pat. Nos. 7,541,728 and7,755,276, incorporated by reference in their entirety herein.

Furthermore, in embodiments, the green phosphor may have a compositiongiven by the formula M_(1−x)Eu_(x)Mg_(1−y)Mn_(y)Al₁₀O₁₇, wherein: M isat least one alkaline earth metal; 0.01<x≦1.0; and 0.01<y≦1.0. Inembodiments, M may be at least one of Ba and Sr, and in embodiments Mmay be Ba. In some embodiments x=1, and furthermore, y may be given by0.1≦y≦0.7, and in embodiments 0.2≦y≦0.4. Examples of phosphorcompositions within the latter range are given by the formulasEu_(1.0)Mg_(0.8)Mn_(0.2)Al₁₀O₁₇, Eu_(1.0)Mg_(0.7)Mn_(0.3)Al₁₀O₁₇ andEu_(1.0)Mg_(0.6)Mn_(0.4)Al₁₀O₁₇.

FIG. 17 is an emission spectrum of a narrow band green phosphor of thepresent invention represented by the formulaEu_(1.0)Mg_(0.8)Mn_(0.2)Al₁₀O₁₇ under excitation by a 400 nm LED; andFIG. 18 is the excitation spectrum of the same phosphor, showingefficient excitation for the green phosphor by a near UV LED emittingradiation at a wavelength of about 300 to 410 nm.

Furthermore, in embodiments, the green phosphor may have a compositiongiven by the formula M_(1−x)Eu_(x)Mg_(1−y)Mn_(y)Al₁₀O₇, wherein M may beat least one of Ba and Sr, and in embodiments M may be Ba, and wherein0.1≦x≦0.5 and 0.2≦y≦0.5, in embodiments 0.3≦x≦0.5 and 0.3≦y≦0.5, and infurther embodiments the composition is given by any one of the secondthrough thirteenth formulas provided in Table 3, including the formulaBa_(0.6)Eu_(0.4)Mg_(0.6)Mn_(0.4)Al₁₀O₁₇.

Table 3 summarizes the testing results of narrow band green phosphors ofthe present invention with general composition ofM_(1−x)Eu_(x)Mg_(1−y)Mn_(y)Al₁₀O₁₇ illuminated by a 400 nm LED—the peakemission wavelength from the photoluminescence curve, the full width athalf maximum (FWHM) of the photoluminesence peak, the CIE coordinatesand the relative brightness (all measured relative to a standard) areall provided.

TABLE 3 Wavelength FWHM Brightness Phosphor (nm) (nm) CIE x CIE y (a.u.)Eu₁Mn_(0.2)Mg_(0.8)Al₁₀O₁₇ 518 29 0.155 0.720 140%Eu_(0.1)Ba_(0.9)Mn_(0.2)Mg_(0.8)Al₁₀O₁₇ 516 26.6 0.140 0.751 110%Eu_(0.1)Ba_(0.9)Mn_(0.3)Mg_(0.7)Al₁₀O₁₇ 517 27 0.147 0.751 110%Eu_(0.1)Ba_(0.9)Mn_(0.4)Mg_(0.6)Al₁₀O₁₇ 517 27 0.153 0.750 94%Eu_(0.2)Ba_(0.8)Mn_(0.3)Mg_(0.7)Al₁₀O₁₇ 517 27.5 0.151 0.747 131%Eu_(0.2)Ba_(0.8)Mn_(0.4)Mg_(0.6)Al₁₀O₁₇ 517 28 0.158 0.749 139%Eu_(0.2)Ba_(0.8)Mn_(0.5)Mg_(0.5)Al₁₀O₁₇ 517.5 29 0.168 0.744 126%Eu_(0.16)Ba_(0.84)Mn_(0.4)Mg_(0.6)Al₁₀O₁₇ 517 28 0.160 0.744 119%Eu_(0.24)Ba_(0.76)Mn_(0.4)Mg_(0.6)Al₁₀O₁₇ 517 28 0.161 0.746 134%Eu_(0.3)Ba_(0.7)Mn_(0.4)Mg_(0.6)Al₁₀O₁₇ 517 28 0.159 0.749 143%Eu_(0.4)Ba_(0.6)Mn_(0.5)Mg_(0.5)Al₁₀O₁₇ 518 28.7 0.167 0.748 150%Eu_(0.4)Ba_(0.6)Mn_(0.4)Mg_(0.6)Al₁₀O₁₇ 518 28 0.167 0.744 163%Eu_(0.5)Ba_(0.5)Mn_(0.4)Mg_(0.6)Al₁₀O₁₇ 519 28 0.166 0.744 163%

In some embodiments the phosphor package comprises at least one narrowband green phosphor with a photoluminescence peak with a full width athalf maximum of less than 60 nm, and wherein the narrow band greenphosphor is configured to emit photoluminescence in wavelengths rangingfrom about 500 nm to about 550 nm under excitation from the a UV sourcewith a wavelength ranging from about 250 nm to about 410 nm.Furthermore, in embodiments the full width at half maximum of thephotoluminescence peak of the at least one narrow band green phosphor isless than 50 nm, in embodiments less than 40 nm, and in some embodimentsless than 30 nm.

In further embodiments, the white light illumination system may includeother green phosphors in addition to, or instead of the narrow bandgreen phosphor described above. Other green phosphors may include: acomposition given by the formula Mn:Zn₂SiO₄; a composition given by theformula Mn:ZnS; a composition given by the formula LaPO₄:Ce,Tb; and acomposition given by the formula (Ce,Tb)MgAl₁₁O₁₉:Ce,Tb. However, theseother narrow band green phosphors do not exhibit as high an excitationefficiency in the UV and near UV part of the spectrum as the exemplarynarrow band green phosphors of the present invention.

Note that the green phosphor a β-SiAlON having a composition given bythe formula Eu²⁺:Si_(6−z)Al_(z)O_(z)N_(8−z) may also be used in thewhite light illumination system of the present invention, although theFWHM of the photoluminescence peak at around 55 nm is not as desirableas the narrow band green phosphors of the present invention such asthose provided in Table 3.

Color LCD Display

Referring to FIG. 19 there is shown a schematic cross-sectionalrepresentation of a color LCD 100 according to embodiments of theinvention. The color LCD 100 comprises a display panel 102 and abacklighting unit 104.

The backlighting unit 104 comprises either a single white light sourceor a plurality of white light sources 106 and a light diffusing plane108. Each white light source 106 is a white light illumination systemsuch as described herein above (FIGS. 11 through 13), that is operableto emit white light with a specified chromaticity color gamut. The lightdiffusing plane 108 ensures the display panel 102 is substantiallyevenly irradiated with white light over its entire surface.

The display panel 102 comprises a transparent (light transmissive) front(light/image emitting) plate 110, a transparent back plate 112 and aliquid crystal (LC) 114 filling the volume between the front and backplates. The front plate 110 comprises a glass plate 116 having on itsunderside, that is the face of the plate facing the LC 114, a firstpolarizing filter layer 118 and then a thin film transistor (TFT) layer120. The back plate 112 comprises a glass plate 122 having a secondpolarizing filter layer 124 and a transparent common electrode plane 126(for example transparent indium tin oxide, ITO) on its upper surfacefacing the LC and a color filter plate 146 on its underside facing thebacklighting unit 104. Additionally, the back plate 112 can furthercomprise a wavelength selective filter 136 located between the colorfilter plate 146 and the backlighting unit 104. The function of thewavelength selective filter plate is described in further detail in U.S.Patent Appl. Pub. No. 2012/0287381, incorporated by reference in itsentirety herein.

The TFT layer 120 comprises an array of TFTs, wherein there is atransistor corresponding to each individual color filter sub-pixel 148,150, 152 of each pixel unit 140 of the color filter plate 146. Typicallythe directions of polarization of the two polarizing filters 118, 124are aligned perpendicular to one another.

The RGB color filters are packaged/configured on the color filter plate146 as illustrated in FIG. 20 which shows a RGB unit pixel 140 of thecolor filter plate 146 comprising a sub-pixel triplet filled by threecolor filters 148, 150, 152. A grid mask (also termed a black matrix)138 of metal, such as for example chromium, defines the color filterelements (sub-pixels) 148, 150, 152 and provides an opaque gap betweenthe sub-pixels and unit pixels. Additionally the black matrix shieldsthe TFTs from stray light and prevents cross-talk between neighboringsub-pixels/unit pixels. To minimize reflection from the black matrix138, a double layer of Cr and CrOx may be used, but of course, thelayers may comprise materials other than Cr and CrOx. The black matrixfilm which can be sputter-deposited underlying or overlying thephotoluminescence material may be patterned using methods that includephotolithography.

In a further embodiment, as illustrated in FIG. 21, the back plate 112further includes a photoluminescence color-elements plate 128. Thecolor-element plate 128 includes an array of red 130 and green 132 lightemitting photoluminescence materials in which each color-elementcorresponds to a respective color sub-pixel in the display. As withembodiment of FIG. 19 the display can further comprise a color filterplate 146 comprising an array of red 148, green 150 and blue 152 colorfilter elements in which each filter element corresponds to a respectivecolor sub-pixel in the display. The color filter plate can be configuredsuch that a red color filter element 148 is positioned overlaying a redphotoluminescence color-element 130 in the color-element plate fordisplaying a red sub-pixel; a green color filter element 150 ispositioned overlaying a green photoluminescence color-element 132 in thecolor-element plate for displaying a green sub-pixel; and a blue colorfilter element 152 is positioned overlaying a blue photoluminescencecolor-element 134 in the color-element plate for displaying a bluesub-pixel. Typically the blue color-element 134 does not include aphotoluminescence material where the backlight comprises a blueexcitation source. In other embodiments the color-elements plate mayinclude a photoluminescence material corresponding to blue sub-pixels ofthe display. The function of the color filter plate 146 is to define thespectral band width of each sub-pixel and to prevent unconvertedexcitation radiation being emitted from pixel areas containing aphotoluminescence material. Such a color filter plate can be especiallybeneficial for photoluminescence displays that utilize quantum dotsmaterials since it can be difficult to guarantee 100% conversion ofexcitation light to photoluminescence light. The color filter plate cancomprise the color filter plate of a known display that uses a whitebacklight. Typically the various filter areas comprise a band passfilter with a pass band corresponding to the color of light emitted byeach pixel area. Such filters not only prevent the transmission ofunconverted excitation radiation but additionally can be used to narrowand/or fine tune the emission color of the pixel areas to optimize theperformance of the display.

In the embodiment illustrated in FIG. 21 the backlighting unit 104comprises a planar light guide (waveguide) 154 with one or more blue andUV co-excitation sources 210 located along one or more edges of thelight guide 154. In operation excitation light is coupled into theedge(s) of the light guide and is guided, by total internal reflection,over the entire volume of the light guide to give a uniform illuminationover the entire surface of the display panel. As shown and to preventthe escape of light from the backlight unit the rear of the light guidecan further comprise a light reflective surface 156.

The photoluminescence material elements in the photoluminescencecolor-elements plate 128 can absorb the excitation blue and UV light andemit light in colors corresponding to the display requirements. Thecolor filter can improve the display by filtering out light in differentcolors, such as the backlight and/or incident light from other colorelements.

Additionally, the back plate 112 can further comprise a wavelengthselective filter 136 positioned between the photoluminescencecolor-elements plate 138 and the backlighting unit 210, and a Hoffmanfilter 158 that can guide the emitted light from photoluminescencecolor-element toward the color filter.

The photoluminescence color-elements plate 128 comprises an array ofdifferent photoluminescence color-elements (sub-pixels) 130, 132, 134which emit red (R), green (G), and blue (B) light respectively inresponse to UV and/or blue excitation radiation from the backlightingunit 210. In some embodiments, only red 130 and green 132photoluminescence materials are incorporated in the photoluminescencecolor-elements plate 128 since the blue excitation light may also serveas the third of the three primary colors that are essential for colorrendering. The photoluminescence materials may be inorganic phosphors,such as described herein above, organic phosphors, and/or materialscomprising quantum dots, all of which emit light of different colors,with a certain spectral width centered at a peak wavelength, whenexcited.

The RGB photoluminescence color-elements can be packaged/configured onthe photoluminescence color-elements plate 138 to correspond with thecolor filters of the color filter plate 146. The arrangement of elementsof the photoluminescence color-elements plate 128 is illustrated in FIG.22 which shows a RGB unit pixel 140 of the photoluminescencecolor-elements plate 128 comprising a sub-pixel triplet filled by twophotoluminescence color-elements 130, 132 with emissions centered at theprimary red (R) and green (G) colors for UV and blue co-excitedphotoluminescence materials, such as phosphors and/or quantum dots. Agrid mask (also termed a black matrix) 138 of metal, such as for examplechromium, defines the photoluminescence color-elements (sub-pixels) 130,132, 134 and provides an opaque gap between the photoluminescencesub-pixels and unit pixels. Additionally the black matrix shields theTFTs from stray light and prevents crosstalk between neighboringsub-pixels/unit pixels. To minimize reflection from the black matrix138, a double layer of Cr and CrOx may be used, but of course, thelayers may comprise materials other than Cr and CrOx. The black matrixfilm which can be sputter-deposited underlying or overlying thephotoluminescence material may be patterned using methods that includephotolithography. As described above, in some embodiments, only red 130and green 132 photoluminescence materials are incorporated in thephotoluminescence color-elements plate 128 since the blue excitationlight may also serve as the third of the three primary colors that areessential for color rendering.

Fabrication of a color display of the present invention as describedabove with reference to FIGS. 19-22, are based on processes well knownto those skilled in the art of LCD display fabrication. Thephotoluminescence color-elements plate 128 may be fabricated using acombination of lithography and deposition techniques known to thoseskilled in the art of display fabrication.

The narrow band green phosphors of the present invention are well suitedto LCD applications due to (1) the emission wavelength being within 10or 20 nm of the center of typical green filters (about 530 nm), and (2)the FWHM of the photoluminescence peak of the narrow band greenphosphors described herein, particularly those phosphors with FWHM ofless than 30 nm, including the phosphors listed in Table 3 above, beingable to fit within the high transmission region (roughly greater than90% transmission) of the typical green filter which extends from about500 nm to about 550 nm.

Although the present invention has been particularly described withreference to certain embodiments thereof, it should be readily apparentto those of ordinary skill in the art that changes and modifications inthe form and details may be made without departing from the spirit andscope of the invention.

What is claimed is:
 1. A white light illumination system comprising: aphosphor package; a first radiation source for providing co-excitationradiation to the phosphor package, the source emitting in wavelengthsranging from about 250 nm to about 410 nm; a second radiation source forproviding co-excitation radiation to the phosphor package, the sourceemitting in wavelengths ranging from about 410 nm to about 540 nm; andwherein the phosphor package is configured to emit photoluminescencecomprising light with wavelengths ranging from about 440 nm to about 700nm upon co-excitation from the first and second radiation sources, andwherein the phosphor package comprises at least one narrow band greenphosphor with a photoluminescence peak with a full width at half maximumof less than 60 nm, and wherein the narrow band green phosphor isconfigured to emit photoluminescence in wavelengths ranging from about500 nm to about 550 nm.
 2. The white light illumination system of claim1, wherein the full width at half maximum of the photoluminescence peakof the at least one narrow band phosphor is less than 50 nm.
 3. Thewhite light illumination system of claim 1, wherein the full width athalf maximum of the photoluminescence peak of the at least one narrowband phosphor is less than 40 nm.
 4. The white light illumination systemof claim 1, wherein the full width at half maximum of thephotoluminescence peak of the at least one narrow band phosphor is lessthan 30 nm.
 5. The white light illumination system of claim 1, whereinthe first radiation source and the second radiation source are part of amulti-chip excitation source.
 6. The white light illumination system ofclaim 1, wherein the green phosphor has a composition given by theformula M_(a)Eu_(1−a)Al_(b)O_(c), wherein: M is at least one divalentmetal selected from the group consisting of Mg, Ca, Sr, Ba, Mn, Zn, Cu,Cd, Sm and Tm; 0<a≦1.0; 0.5≦b≦12.0; and 1.75≦c≦19.0.
 7. The white lightillumination system of claim 1, wherein the green phosphor has acomposition given by the formula M_(1−x)Eu_(x)Mg_(1−y)Mn_(y)Al₁₀O₁₇,wherein: M is at least one alkaline earth metal; 0.01<x≦1.0; and0.01<y≦1.0.
 8. The white light illumination system of claim 7, whereinx=1.
 9. The white light illumination system of claim 8, wherein0.1≦y≦0.7.
 10. The white light illumination system of claim 8, wherein0.2≦y≦0.4.
 11. The white light illumination system of claim 7, wherein Mis at least one of Ba and Sr.
 12. The white light illumination system ofclaim 11, wherein 0.1≦x≦0.5 and 0.25≦y≦0.5.
 13. The white lightillumination system of claim 11, wherein 0.3≦x≦0.5 and 0.3≦y≦0.5. 14.The white light illumination system of claim 7, wherein the compositionis given by the formula Ba_(0.6)Eu_(0.4)Mg_(0.6)Mn_(0.4)Al₁₀O₁₇.
 15. Thewhite light illumination system of claim 1, wherein the phosphor packagefurther comprises a red phosphor configured to emit photoluminescence inwavelengths ranging from about 600 nm to about 700 nm.
 16. The whitelight illumination system of claim 15, wherein the white lightillumination emitted by the system covers an area including greater than90% of NTSC 1953 color gamut specification as mapped on CIE 1931 xychromaticity diagram.
 17. The white light illumination system of claim15, wherein the green phosphor has chromaticity coordinates CIE (x, y)within an area of CIE 1931 xy chromaticity diagram defined by a simplequadrilateral with vertices (0.120, 0.775), (0.230, 0.755), (0.360,0.620) and (0.150, 0.650).
 18. The white light illumination system ofclaim 15, wherein the green phosphor has chromaticity coordinates CIE(x, y) within an area of CIE 1931 xy chromaticity diagram defined by asimple quadrilateral with vertices (0.128, 0.768), (0.205, 0.753),(0.278, 0.660) and (0.150, 0.680).
 19. The white light illuminationsystem of claim 15, wherein the green phosphor has chromaticitycoordinates CIE (x, y) within an area of CIE 1931 xy chromaticitydiagram defined by a simple quadrilateral with vertices (0.135, 0.760),(0.180, 0.750), (0.195, 0.700) and (0.150, 0.710).
 20. The white lightillumination system of claim 15, wherein the red phosphor haschromaticity coordinates CIE (x, y) within an area of CIE 1931 xychromaticity diagram defined by a simple quadrilateral with vertices(0.61, 0.39), (0.70, 0.30), (0.68, 0.30) and (0.59, 0.39).
 21. The whitelight illumination system of claim 1, wherein the first radiation sourceemits in wavelengths ranging from about 390 nm to about 410 nm.
 22. Thewhite light illumination system of claim 1, wherein the second radiationsource emits in wavelengths ranging from about 445 nm to about 455 nm.23. The white light illumination system of claim 1, wherein the phosphorpackage is encapsulated with the first and second radiation sources. 24.The white light illumination system of claim 1, wherein the phosphorpackage is remote from the first and second radiation sources.
 25. Thewhite light illumination system of claim 1, wherein the white lightillumination system is a display backlighting system.
 26. The whitelight illumination system of claim 1, wherein a final light productgenerated by the white light illumination system comprisesphotoluminescence from the phosphor package and light generated by thesecond radiation source, but not light generated by the first radiationsource.
 27. A white light illumination system comprising: a phosphorpackage; a first radiation source for providing co-excitation radiationto the phosphor package, the source emitting in wavelengths ranging fromabout 250 nm to about 410 nm; a second radiation source for providingco-excitation radiation to the phosphor package, the source emitting inwavelengths ranging from about 410 nm to about 540 nm; and wherein thephosphor package is configured to emit photoluminescence comprisinglight with wavelengths ranging from about 440 nm to about 700 nm uponco-excitation from the first and second radiation sources, and whereinthe phosphor package comprises a green phosphor with chromaticitycoordinates CIE (x, y) within an area of CIE 1931 xy chromaticitydiagram defined by a simple quadrilateral with vertices (0.61, 0.39),(0.70, 0.30), (0.68, 0.30) and (0.59, 0.39).
 28. The white lightillumination system of claim 27, wherein said phosphor package furthercomprises a red phosphor, said red phosphor having chromaticitycoordinates CIE (x, y) within an area of CIE 1931 xy chromaticitydiagram defined by a simple quadrilateral with vertices (0.61, 0.39),(0.70, 0.30), (0.68, 0.30) and (0.59, 0.39).
 29. A color displaycomprising: a display panel comprising a plurality of red, green andblue pixel areas; a white light illumination system; and a color filterplate located on a side of the display panel that is distal to the whitelight illumination system, wherein the color filter plate comprises atleast one of: first filter areas corresponding to red pixel areas of thedisplay that are operable to allow the passage of red light; secondfilter areas corresponding to green pixel areas of the display that areoperable to allow the passage of green light; and third filter areascorresponding to blue pixel areas of the display that are operable toallow the passage of blue light; wherein the white light illuminationsystem comprises: a phosphor package; a first radiation source forproviding co-excitation radiation to the phosphor package, the sourceemitting in wavelengths ranging from about 250 nm to about 410 nm; asecond radiation source for providing co-excitation radiation to thephosphor package, the source emitting in wavelengths ranging from about410 nm to about 540 nm; and wherein the phosphor package is configuredto emit photoluminescence in wavelengths ranging from about 440 nm toabout 700 nm upon co-excitation from the first and second radiationsources, and wherein the phosphor package comprises at least one narrowband green phosphor with a photoluminescence peak with a full width athalf maximum of less than 60 nm, and wherein the narrow band greenphosphor is configured to emit photoluminescence in wavelengths rangingfrom about 500 nm to about 550 nm.
 30. A photoluminescence color displaycomprising: a display panel comprising a plurality of red, green andblue pixel areas; an excitation source operable to generate excitationradiation for operating the display, said excitation source comprising:a first radiation source emitting in wavelengths ranging from about 250nm to about 410 nm; a second radiation source emitting in wavelengthsranging from about 410 nm to about 540 nm; a photoluminescencecolor-elements plate comprising at least one of: a firstphotoluminescence material corresponding to red pixel areas of thedisplay that is operable to emit red light in response to saidexcitation radiation; a second photoluminescence material correspondingto green pixel areas of the display that is operable to emit green lightin response to said excitation radiation; and a third photoluminescencematerial corresponding to blue pixel areas of the display that isoperable to emit blue light in response to said excitation radiation;and a color filter plate located on a side of the display panel that isdistal to the white light illumination system, wherein the color filterplate comprises at least one of: first filter areas corresponding to redpixel areas of the display that are operable to allow the passage of redlight; second filter areas corresponding to green pixel areas of thedisplay that are operable to allow the passage of green light; and thirdfilter areas corresponding to blue pixel areas of the display that areoperable to allow the passage of blue light; wherein the secondphotoluminescence material comprises at least one narrow band greenphosphor with a photoluminescence peak with a full width at half maximumof less than 60 nm, and wherein the narrow band green phosphor isconfigured to emit photoluminescence in wavelengths ranging from about500 nm to about 550 nm.